Parametrized post-Newtonian limit of fourth order gravity inspired by scalar-tensor gravity

Based on the dynamical equivalence between higher order gravity and scalar-tensor gravity the parametrized post-Newtonian (PPN) limit of fourth order gravity is discussed. We exploit this analogy developing a fourth order gravity version of the Eddington PPN parameters. As a result, Solar System experiments can be reconciled with higher order gravity, if physical constraints descending from experiments are fulfilled.